Significant Accounting Policy Other (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Impairment of Oil and Gas Properties	$ 0	$ 828,905	$ 0
Exploration and Production Costs	14,519	$ 10,120	$ 23,355
Proved Developed [Member]
Property, Plant and Equipment [Line Items]
Impairment of Oil and Gas Properties	824,742
proved undeveloped [Member]
Property, Plant and Equipment [Line Items]
Impairment of Oil and Gas Properties	$ 4,163